Resistance element for hydrocarbon cracking processes



May 1932- R, ER

RESISTANCE ELEMENT FOR HYDROCARBON CRACKING PROCESSES Filed Feb. 12,1929 glwum M01,

Patented May 24, 1932 1,860,322

UNITED STATES PATENT OFFICE RUSSELL CARTER, OF WASHINGTON, DISTRICT OFCOLUMBIA RESISTANCE ELEMENT FOR HYDROCABBON CRACKING PROCESSESApplication filed February 12, 1929. Serial No. 339,462.

This invention relates to improvements in cracking temperature. In thisconnection, it the art of recovering hydrocarbon values, and has beenproposed more or less successfully more particularly to the electricalrecovery to employ a tubular casing surrounding the of hydrogeneous andcarbonaceous values resistance unit comprising the electrical heatfromhydrocarbonsources. ing unit to prevent direct contact and re- Theprimary object in view is the maxisulting injury, but such proposedmanner of mum efliciency in heat conservation and (lisheating has notbecome popular because of tribution. uncompensated and preclusive heatlosses.

A more detailed object is the preservation The present inventionobviates the difiiculm of the resistance of the heating unit contiesthus presented by providing for the imstantly at high efficiency whilepermitting mediate contact of the oil or other hydrocar direct contactof the hydrocarbon sources hon source with the electrical resistanceunit, with such unit. and in greater detail includes 'l1 sthel1 at ngunitre iOuS attempts attaining and maintaining such efficiency toaccomplish this result have not been suc- 15 while the hydrocarbonsources are approachcessful commercially because carbonization ing andat cracking temperature under the of oil has inevitably occurred alongthose influence of the heat. from the heating unit. S rf s of th h a ingn t in Conta t With A still further object in view is the provithe oil,and the resistance of the heatin unit sion for the readily detachablemounting of has thus been lowered to an extent ren ering 13 a heatinunit in such location as to receive the Unit iIlCH lflble 0f affordin ithe re uisite h direct contact of the hydrocarbon sources eflt- TheCarlJoIliZat On referred to haS 00- while providing etfectivc electricalcontact u d I t m rely p rficially but 011 the with the h atin unit,surfaces within the interstices of the heating lVith these and otherobjects in view as nit, so as to form Within the heating unit will inpart hereinafter become apparent and self a path of relatively lowresistance for in part be stated the invention comprises the eleetrlc eboth the art or process of treatment for prep h P e t iI e iOI1 obviatessuch difaration of electrical resistance units, the imficlllties byprotecting the heating unit proved mode of recovering hydrocarbon g s aCondition enabling formation of values, and also the apparatus producede h r occ uded or surface carbon Within the thereby and utilized th r isubstance or interstices of the resistance unit. In the accompanying(lra\vings, To this end, the present invention includes Figure 1 is afragmentary, sectional plan providing a resistance bar formed of carboofa structure embodying the features of the nduln crystals located in theshape of a bar 33 present invention. and caused to adhere eitherbyrecrystalliza- Figure 2 is an enlarged, detailed similar tion or bythe use of a binder. The'recrystalsection. lization is preferablyeffected by electrical Figure 3 is a transverse section taken on fusing.Care should be exercised to employ the plane indicated by line 3-3 ofFigure such uniformity of pulverized carborundum,

"- 2, and looking in the direction indicated by the original 'crvstals,that the recrystallization the arrows. will afford substantiallyuniform electrical In the recovery of hydrocarbon values resistance atall points throughout the length from such hydrocarbon sources as heavyoils, of the bar and not provide a spot or area H it is common practiceto raise the oil to crackhaving a higher or lower resistance than anying temperature, recover the escaping volaother part which would resultin localization tiles. and condense the same for the producofintensified heat during action. The same tion of the lighter hydrocarbonfuels; and precaution must be taken When a binder is it has beenheretofore proposed to move a employed, so that the resistance will beunir column of such fuel past an electrical heatform throughout thelength of the barand ing unit to bring the fuel to the requisite in allparts thereof. The thus produced carborundum bar is preferablyconstructed to offer a resistance of approximately fifty ohms per cubiccentimeter at a temperature of 25 Such a completed bar is'indicated at 1in the accompanying drawings, and to mount such a bar effectively incircuit while detachably arranged within a stream. of fluid sources ofhydrocarbon values may be successfully effected only with the exerciseof care and precision, first, to insure electrical contact at therespective ends of the bar in a manner to avoid arcing, and, second, toso provide such contact as to enable ready assemblage and dismantlingwhile preserving the bar out of electrical contact with the surroundingcasing or tube during use. To this end, the details illustrated in theaccompanying drawings are preferably utilized by me, including theproviding of a metal cap 2 for each end of the bar which is preferablycemented to the bar by appropriate contact producing means ofsufficiently lower re sistance than the bar to avoid injury to thecement during use. The cement is indicated at 3 and preferably consistsof a moist paste applied within the cap 2 or on the end of the bar 1just before the assemblage of the cap on the bar. The paste or cement 3may be of Various acceptable substances, and I have found a putty-likeconsistency of a mixture of litharge, glycerine, and pulverized carbon(lamp black or the likeyrquite effective. Just before applying the cap 2to the end of the bar 1, a sleeve 1 is extended through an aperture 5 inthe cap 2, and the end of the sleeve 4 within the cap is burred orswaged out at 6 to form a retaining head. The terminal portion of sleeve4 may be slit to facilitate the formation of the head 6. The cap 2 ispreferably provided with internal threads v7, and when applied with thesleeve 4 in place and the paste 3 already applied, the cap and the bar 1are rotated relative to each other so that partial screw threads areformed on the bar by the thread 7, and the cap is brought to aneffectively seated posi tion with an especially successful electricalnon-arcing contact between the sleeve 4 and the bar 1. I

In Figure 2 of the drawings is seen a somewhat idealized condition ofthe thread 7 and its formed threads in bar 1 with the contactimproving,low-resistance paste or cement 3, therebetween. While it is understoodthat such clearcut threaded connection as shown in Figure 2 is quitedesirable, nevertheless it frequently happens that the threads on bar 1will not be entirely perfect and may be far from perfect while, at thesame time. affording rigid and effective anchorage and mechanicalconnection sufficiently sturdy for withstanding application andoperation stresses and shock. The threads or partial threads on bar 1will also add to the efficacy When the bar 1 has been thus completedwith its terminals provided, it is ready to be conditioned to enable itto avoid resistancechanging carbonization during use. To obtain thisresult, the bar 1 and its terminals,

including caps 2 and sleeves 4;, are covered with a coating 20 of anespecially provided coating material. Such coating material preferablyconsists of a mixture of fire clay, silica, and sodium silicate. Thesilica is preferably of a very fine gauge of comminuted particles, andthe fire clay is preferably of the kind containing magnesium chloride.The proportions preferred, by weight, are from 1 to 3 per cent. sodiumsilicate, ap proximately 40 per cent. powdered fire clay, and from 57per cent. to 59 per cent. finely comminuted silica. The object in mindis the production of a coating on the bar 1 that will have aparticularly high modicum of stability under thermic variations. Thesilicate of sodium causes the formation on the finished coating ofasubstantially impervious surface,

and the proportions of fire clay and silica are varied, according to themagnesium chloride content of the fire clay. less silica being used inthe absence or reduction in the quantity of magnesium chloride present.The amount of silica employed is varied to provide the requisite balancefor causing the finished coating to possess maximum stability at hightemperatures and to resist bulk variations expansions and contractions)under the influence of heat variations. Also, in the preparation of themixture, the fire clay is used in proportions to provide a close textureof the finished coating especially adapted to resist erosion and toinsure interfillingaccessible interstices at or near the surface of thebar 1. The mixture is moistened with water and thoroughly triturated toreduce it to a creamy consistency so as to provide as nearly imperviousand smooth coating as possible, and is then flowed onto the bar 1 andits connections 2 and 4. This may be done by a brush or by dipping thebar in a bath of the creamy mix ture. After the first application to thebar 1. the bar is dried in an oven, or otherwise slowly baked to avoidcracking or disruption of the superficial finished or smooth surfacefrom ebullitions or escaping steam. As soon as the first application hasbeen dried, a second coat of the same material is applied and the baragain baked: and it is preferable to then apply a third coat so that thefinished coating is in fact made up of a series of layers. After thelast layer has been applied and baked the whole bar and its coating aresubjected to a temperature of approximately 2,000 F. This may be done inany conlit) '9 and venient manner, as, for example, hooking .the barinto the requisite electrical circuit to electrically raise the bar tothe required temperature. This high temperature causes the material ofthe coating to penetrate the barsufi'iciently to effectively resistsubsequent penetration thereof by carbon deposits in the oil stream.Since the regular use of the bar does not require any such hightemperature as 2,000 F. the fixing of the coating by this temperatureinsures capacity of the completed article to withstand all the regularoperating temperatures.

Also, it should be noted that the coating made up of the mixture setforth, or appropriate variations thereof, after having been subjected tothe high temperature, will not crack or spall, and the selection ofmaterials for the coating mixture is made with this in mind.

In applying the bar 1 as the unit of resistance in actual practice forcracking hydrocarbon oils, a series of tube sections 8 is provided, onefor each bar 1, and the several tube sections 8 are arrangedhorizontally and coupled preferably in multiple by cross nipples 9, 9,connecting the end of one section 8 at one side to the end of theadjacent section 8 and connecting the opposite end of the same section 8at the other side to the corresponding opposite end of the next sectionat that side, so that the through a section 8 will pass across thenipple move in the opposite direction through the next section 8 fromthe direction of its flow in the former, and thus throughout a. seriesof such sections sufficient in number to insure the requisite raisingand maintenance of cracking temperature of the oil. As a matter-ofconvenience and facility of assemblage, each section 8 may consist of alength of pipe having at each end an ordinary T-fitting 10, one end ofwhich engages the section 8, the shank of which receives the nipple 9,and the other end of which receives the threaded end 11 of a plug 12. Asa matter of mechanical expediency and convenience, a bushing 13 may beinterposed between the threaded end 11 of plug 12 and the engaged end ofthe T-fitting 10. The plug 12 is quite similar in mechanicalconstruction to the ordinary spark plug employed in internal combustionengines except that the metallic casing indicated in the drawingsas 12forms no part of the circuit, and there is, of course, provision againstrather than provision for an arc or jump spark. -Within the plug 12 isarranged an insulator or porcelain 13 through which extends a contactrod 14. The porcelain 13 at its inner terminal portion is provided witha tubular enlargement 15. The rod 14 is provided with a head 16 at theouter end of the recess 15 to sealthe passageway through which the rodextends to the exterior so as stream of oil flowing distance beyond theinner end of the porcelain 13, and the section 8 is proportioned inlength to the length of the respective bar 1 to lie. between the innerends of the two contact rods 14 for the respective section 8 withoutcontact therewith. However, the sleeves 4 are proportioned and locatedto snugly receive the inwardly extending end portions of rods 14 and toextend into the respective recesses 15. The contact betwen the sleeves 4and inner terminal portions 14 is sufficiently close to provideeffective electrical contact and also to provide sufficient mechanicalconnection and support to sustain the bar 1 in its proper relation insection 8.

Assemblage is effected by positioning the extended inner end portion ofa rod 14 Withinthe sleeve 4 of a complete bar assemblage 1, and theninserting the said bar assemblage endwise through the section 8 untilthe plug 12 carrying the last-named rod 14 is threaded into the bushing13. hen this has been done, the operator starts to insert a plug in theremaining open end of the opposite T- fitting 10, but in doing so firstcauses the inner end of the rod 14 to find its Way into the exposed endof the exposed sleeve 4. As soonv as this coupled connection is started,the operator may screw both plugs 12 to their finally seated positionwith assurance that the parts are properly assembled and will remain inproper relation during operation.

When the parts have been thus assembled, the outer ends of rods 14 areclamped or otherwise effectively hooked to the bus wires 18. 18, orother appropriate source of current, as byclamping nuts 19, 19, orotherwise as preferred.

It will be observed that the parts thus assembled are well adapted foreasy and quick disassembling, replacement, and reassembling.

\Vhen all of the several units have been assembled as stated, electriccurrent will be supplied to bars 1, and oil under the requisite pressuredirected through sections 8 and their connections. A column of oil willthus move continuously along the several resistance bars 1 until raisedto the cracking temperature and will then be discharged into the usualexpansion chamber, not illustrated, for further treatment. The plant maybe left on stream practically indefinitely, so far as the units 1 areconcerned, and a very high degree of efficiency in heat conservation anddistribution is obtained, because notwithstanding the direct contact ofthe oil with the several resistance bars 1 the said bars maintain theirstandard high resistance. Carbon particles which are precipitated duraing cracking and mingled with the stream present invention.

will not find lodgment or effect a condition of the several resistancebars 1 "tending to reduce the resistance thereof or of any portionthereof.

Among the many objects of the present invention is included demonstrablethermal efficiency when the heating units are properly heat insulated,which efiiciency compares favorably with other forms of fuel heating ofcracking oils, and at the same time by the present improved electricalapparatus the dangers attending heating of liquid hydrocarbon to hightemperatures under high pressure with an open fire are eliminated.

While a specific embodiment is illustrated and specified herein indetail, it will be readily understood thatmodifications in detail may bemade almost without limit while incorpo- .;\.rating and adhering to thesubstance of the For instance. though 'a -multip1e arrangement of tubingis illustrated, it is quite obvious that other arrangements may beemployed while affording the advantages of the present invention.Subject to those limitations of available space and other controllingfactors and specific requirements of a given or individual instance,other arrangements of details than those illustrated and described maywell be utilized advantageously and in some instances preferably to thespecific form set forth.

It will be observed that each bar 1 is proportioned in length withrespect to the length of the respective section 8 such that the sleeves4 extend across the greater part of the cross current of oil to or fromthe nipples 9, and, accordingly, provide ample area to avoid contact ofany possible deposits of carbon at the places of change in the directionof flow of the oil What is claimed is 1. In apparatus for heatinghydrocarbon material, an electrical resistance adapted for directcontact with hydrocarbon sources during heating and maintenance thereofto and at a relatively high temperature comprising a member ofelectrical resistance material and a carbon-deposit resisting coating onsaid member, of fire-clay, silica, and sodium silicate.

2. The art of producing an electrical heating unit adapted for remainingsubstantially constant in its resistance capacity while in directcontact with hydrocarbon sources during heating of said sources tocracking temperature comprising forming an electrical resistance member,and coating the member with a silicious covering and raising the memberand covering to a temperature higher than the maximum temperatureemployed in the heating of the hydrocarbon sources.

8. The art of producing an electrical heating unit adapted for remainingsubstantially constant in its resistance capacity while in directcontact with hydrocarbon sources during heating of said sources tocracking temperature comprising forming a member of electricalresistance material, and coating the member with a mixture of fire-clay,silica, and sodium silicate sufliciently for preserving the memberagainst deterioration in its resistance at cracking temperature.

4. The art of producing an electrical heating unit adapted for remainingsubstantially constant in its resistance capacity while in directcontact with hydrocarbon sourcesduring heating of said sources tocracking temperature comprising forming a bar of carbonaceous crystals,covering the bar with a carbon deposit-resisting coating, baking thecoating on the bar at a temperature and rate sufficiently low and slowto avoid disruption and deformation of parts of the coating, andthereafter raising the temperature of the coating temporarily to atemperature exceeding the maximum temperature of the bar during regularuse.

5. In the art of producing an electrical heating unit, the steps offlowing a creamy consistency of sodium silicate, fire-clay, and silicaonto an electrical resistance bar, drying the coating on the bar whileavoiding cracking or disruption thereof, applying a second coating onthe first coating, and baking the bar and its coatings at a temperaturein excess of cracking temperature of hydrocarbon materials.

In testimony whereof I alfix my signature.

RUSSELL CARTER.

